Assembly cell and control sequence verified on a digital twin
Period: 2026.06 – 08Stage: Design and model verification
- Project
- Drive-wheel assembly cell design & control-logic verification
- Company
- 로보톰robotic furniture manufacturer
- Scope
- Virtual environment and control modelPLC and physical cell to follow
Two-stage cell processMotor and reducer pre-assembly → Final wheel assembly
A CAD assemblability review, an Isaac Sim virtual environment and a Python control model, each built and verified, gave the design decisions a basis before any equipment investment.
Pre-verification results · investment and control-design effects
| Indicator | Result | Basis |
|---|---|---|
| Lower investment riskDesign review before equipment introduction | Less rework and opportunity cost | Design alternatives reviewed in advance on the digital twin and in CAD |
| Sequence reliabilityNormal and exception behavior reviewed | Stronger control reliability | 53 normal, alarm and maintenance model tests passed |
| Lower loss riskAssembly order and layout review | Less risk of changes after introduction | 1 unassemblable case foundlayout change drawn up |
Challenge
- Assembling one complete product took 1–2 days for one skilled worker
- Assemblability and sequence needed checking before equipment investment, to prevent trial and error and cost losses
Work carried out
Digital-twin environment
A CAD-based virtual process, equipment layout and verification environment
Assemblability and process layout review
Two-stage cell design, snap-ring interference found, assembly units regrouped
Control sequence development and verification
53 normal, alarm and maintenance scenarios tested on a Python model
Design decisions
- Redesign and rework risks checked by virtual verification before anything is built
- Designed so repetitive assembly is automated and exceptions and failure effects are kept separate
- Scope of work
- End to end on my own · digital-twin, process and control-model design
- CAD review, sequence tests, 3D visualization, documentation
- Coordination
- Reflected input from the floor when choosing the drive-wheel specification
- Applied skills
- Cell process design
- SOLIDWORKS
- Python
- Isaac Sim
- Blender
Drawings & pre-verification
From an interference found to regrouped assembly units and a verified sequence
A design decision changed before equipment investment
Snap-ring pre-fit interference found → coupling sub-assembly regrouped
An assembly problem that would have been fixed after manufacture was reviewed before investment
Control-model verification
Python control model · 53 normal, alarm and maintenance scenarios passed
Basis: Python unit testsintegration of the changed CAD assembly, the PLC simulator and the physical cell come in later verification
- Scope
- Digital-twin environment
- CAD assemblability review
- Control-sequence verification
- Later verification
- PLC simulator
- Physical cell and PLC
Control-model tests & evidence
Control sequence verified against stated normal and exception conditions
Checked on the Python model that wrong follow-on actions are blocked when a precondition is missing, the mode changes or an alarm is reset
53 / 53Python control-model tests passed
- Assembly sequence and evidence conditions
- 16 / 16
- Operating modes and transitions
- 9 / 9
- Alarm and recovery conditions
- 18 / 18
- Maintenance reverse motion and no-replay
- 10 / 10
| Input and test situation | Expected behavior and criterion | Result |
|---|---|---|
| Preceding assembly unfinishedFollow-on action requested without the assembly-done condition | The request is blocked and the done state is not changed | PASSno command issued, done state kept |
| Mode change during motionSwitch from automatic to semi-automatic mode | The running command is cancelled and the model moves to the diagnostic state · the old command is never replayed automatically | PASScommand released, replay blocked |
| Reset after an alarmCause still present, recovery condition unmet, then met, entered in turn | Reset is allowed only after the cause is cleared and recovery is met · a reset alone never restarts motion | PASSreset and restart blocked per condition |
Basis: the existing control model, 4 test files and the verification specification. On 2026.10.20 all 53 tests were rerun on a separate copy and passed. The table summarizes the inputs and criteria of representative cases.
CAD · assemblability review
Snap-ring interference found · sub-assembly change drawn up
Isaac Sim · environment
CAD → USD conversion · virtual process and equipment layout
Python · model tests
Control states and command conditions verified · 53 regression tests passed
Later · integrated verification
Changed assembly and PLC connection · physical motion and physics verification
Design renders
The digital-twin environment and the assembly-cell layout
Factory layout
- Servo assembly cell
- Frame assembly cell
- Vision and torque inspection
- Inbound and outbound path
A silent virtual render video. Seen at an angle from above, the two clamps fix the drive-wheel assembly on the test jig, the guard closes, and the wheel turns.
Disclosure scope Virtual render 3 · Virtual render video 1 · CAD drawing 2 · Diagram 2. The renders and the render video are virtual models, and the drawings are the geometry of the SOLIDWORKS CAD. Values shown inside the renders are examples.
For more material, please ask by e-mail.
fpdlsdk3115@gmail.com